PROPERTIES OF ORES USED IN MAKING CAST IRON. 33 Bessemer iron, owing to such being very low in phosphorus. Aside from the iron being low (see Chapter XXXIV.), it is mainly the phosphorus that is to be feared in mill cinder iron, as this cannot well be eliminated. If the "iron" is lower and the phosphorus higher than is beneficial in pig metal there are grounds for rejecting it, but otherwise the foundryman is rarely justified in condemning mill cinder mixed pig iron on the ground that it contains slag because cinder was used in making the iron, until he has tested it to have a knowledge of its chemical constituents and physical properties. Founders have used mill cinder mixed pig iron when they thought there had not been an ounce of cinder mixed with the ore. Not only is mill cinder mixed with ores, but a furnace has been kept going steadily making pig metal with simply all mill cinder. Mr. C. I. Rader has clone this at the Sheridan Furnace, Sheridan, Pa., in making forge or mill iron.ontained in the cinder ore where all cinder was used.